As best as I can tell here is a rough definition for their most frequent terms:
- Yesterday - before they woke up most recently. This could be right before their nap, the day before, last week, last month or any time in the past.
- Tomorrow - any time in the future. It could be later today or in a few years.
- Soon - usually before they go to sleep again.
- Last night - any night in the past.
- This morning - any time in the past. It could be a few minutes ago, yesterday or any day before that.
Today is the tomorrow you worried about yesterday